本土新穎嗜熱抗輻射菌株NTU-1233醣脂質之結構判定

Abstract

根據先前的研究指出，醣脂質為嗜熱性微生物之細胞表面的主要成分，但是造成此現象的分子機制至今仍舊沒有完整的定論。由於嗜熱性微生物本身的棲息環境溫度較高，造就了其細胞表面醣脂質之化學結構的特異性與多樣性，因此嗜熱性微生物的醣脂質長久以來都是被研究的目標。本研究主要針對由台灣一嗜熱抗輻射本土菌株 NTU-1233 所萃取出來之細胞表面醣脂質做結構之解析。實驗首先將以下五株本土菌株 NTU-484、NTU-1233、NTU-1085、NTU-1089、NTU-407及兩株標準菌株 Truepera radiovitrix、Deinococcus murrayi 共七株菌株的醣脂質粗萃物對小鼠巨噬細胞進行刺激以分泌腫瘤壞死因子 TNF-α，發現其中 NTU-1233 的醣脂質粗萃物對小鼠巨噬細胞有著較強的刺激性。NTU-1233 的醣脂質粗萃物經純化後得到三個物質以化學分析、薄膜層析 (TLC)、核磁共振分析 (氫譜、碳譜、TOCSY、HSQC、HMBC)、質譜分析（氣相層析質譜、電噴灑游離質譜、基質輔助雷射脫附游離質譜）後得以判讀出以下三個醣脂質之化學結構，分別為兩個硫脂質，sulfoquinovosyl diacylglycerol (SQDG)、2’-O-acyl-sulfoquinovosyl diacylglycerol (ASQD)；一個神經鞘脂 α-N-acetyl-glucosaminyl-(1-3)- β galactosyl-(1-1’)-dihydroceramid (GlcNAcα3GalβCer)。根據氫譜，此三個醣脂質之脂肪酸上的長碳鏈皆為飽和鍵。在本研究中，提出了兩個第一次的發現，分別是第一次發現非光合生物中存在有 ASQD 以及發現新物質 GlcNAcα3GalβCer。

According to previous studies, glycolipids are the major components present in the cell surface of thermophilic bacteria. The high proportion of glycolipids in the cell membranes could possibly to contribute to the ability of the bacteria to grow at high temperature, however, the molecular basis of this phenomenon is still unclear. The structure of glycolipid of thermophilic bacteria has long been a topic and has been proved to exhibit great structural diversity due to its high temperature growth condition. This study focuses on the structural analyses of glycolipids isolated from this new indigenous of Taiwan, NTU-1233. Lipid crude extracts from two type strains, Truepera radiovitrix and Deinococcus murrayi; and five indigenous strains, NTU-484, NTU-1233, NTU-1085, NTU-1089, NTU-407 were subjected to TNF-α induction assay and found that lipid crude extracts of NTU-1233 exhibits stronger immunostimulation activity. The structures of three major glycolipids purified from lipid crude extracts of NTU-1233 were determined using TLC, NMR spectroscopy (TOCSY, COSY, HSQC, HMBC), GC-MS, MALDI-MS and ESI-MS, and chemical analyses. According to the spectroscopic and chemical analyses, the structures of three glycolipids are elucidated to be two sulfolipids sulfoquinovosyl diacylglycerol [SQDG] and its acylated derivative, 2’-O-acyl-sulfoquinovosyl diacylglycerol [ASQD], and a novel sphingolipid, glucosaminyl(1-3)-β-galactosyl-(1-1’)-dihydroceramide [GlcNAcα3Galβ- Cer]. The acyl chain of fatty acid moiety of these three glycolipids are saturated according NMR analysis. It is the first time for ASQD to be found in nonphotosynthetic organism, and for GlcNAcα3GalβCer, it is a novel compound that has never been reported before.